Developing a complex system requires partitioning the target system into several subsystems. It is generally difficult to define each subsystem's scope and functional requirements as well as data dependencies among subsystems. Requirements Integration Model (RIM), which consists of a workflow model and a work procedure, can provide specific guidelines and techniques to increase quality of requirements obtained under a time constraint. We have applied the technique to the implementation of the educational system for the Department of Computer Engineering at Chulalongkorn University, Thailand. Experiences from this case study have shown that the model can assist developers to clearly specify functional requirements for each subsystem and to identify data dependencies among subsystems.